The present invention relates to pressure/vacuum transducers. More particularly, the present invention relates to pressure/vacuum transducers for use in high purity applications.
Pressure/vacuum transducers are known. Such devices typically couple to a source of pressure or vacuum; generate an electrical characteristic that varies according to the pressure or vacuum; and provide an electrical representation of the varied electrical characteristic such that the vacuum or pressure can be known to an operator, or other parts of the process.
High purity pressure or vacuum transducers are a relatively small subset of general vacuum or pressure transducers. These devices are specifically adapted for exposure to extremely delicate and/or very clean processes. These are the types of processes where a particle breaking from the pressure transducer or even outgassing therefrom could have a deleterious effect on an entire processing line. One example of such an application is semiconductor processing.
Vacuum transducers for high purity applications involving, for example, the deposition or removal (etching) of materials, such as in the semiconductor industry, are frequently heated for a couple of reasons. First, such vacuum transducers are heated to potentially reduce the amount of deposited or etched material that accumulates on the vacuum sensor in the transducer. Additionally, known vacuum sensors and associated components are temperature sensitive, thus requiring the temperature of the transducer to be precisely controlled with a fully integrated heater. The integrated heater ensures that both the vacuum sensor and the associated components are maintained at the precisely controlled temperature.
The arrangement of an integrated heater maintaining a precise temperature of both the vacuum sensor and associated components has generated a number of problems in the art. For example, the integrated nature of the heater requires that the suppliers and customers of such devices carry an inventory of non-heated transducers as well as heated transducers often covering two to three temperature ranges. This requires three to four times the inventory of non-heated transducers alone, thus generating a much higher inventory than would be required if fully-integrated heaters were not required. Another problem of current designs is that customers must decide when they purchase the vacuum transducer, exactly where the transducer is going and what level of heating, if any, will be needed. A non-heated vacuum transducer simply cannot be transformed into a heated transducer. Thus, current designs are not scalable to the varying applications to which customers would wish to apply them. Yet another problem with current designs is that customers wishing to evaluate the effect of heating at various temperatures on a vacuum transducer for a given process must purchase a different transducer for each temperature to be evaluated. Customers generally may try different heaters on a single vacuum transducer alone and note the effects. Thus, simply attempting to determine which transducer to use will often generate the additional cost of purchasing one or more useless (at least for that application) vacuum transducers as well as the additional time of removing and installing various transducers during the process. Another problem with current designs is that the heater is integrated in the same housing as the sensor and electronics. This means that the electronics are constantly exposed to a higher temperature, which limits their useful life.